It is not clear how to disentangle the variation in the signal
coming from optical-depth effects and from accretion-rate variations.
Variability in the accretion rate (item (i) above) is expected over a wide range of timescales but it decreases towards short timescales [1]}. Therefore, the accretion rate might show only small variations over a rotational period, but both high-resolution simulations and monitoring campaigns will be needed to assess this in detail.
Also, if the accretion rate and mass are such that extinction
is absent or negligible, variations in the H \(\alpha \)  signal would be due
only to variations in the accretion rate, for instance due to episodic accretion [2]}, [3]}, [4]}, which might not be periodic,
or to rotational modulation of the accretion features (e.g. hot spots),
which would be periodic. Ideally,
this could help distinguish the source of the variability while
providing constraints on the spin rate of young objects
[5]}, [6]}, [7]}.
